Pregnant or not

I really need some advice. I never use protection with my boyfriend. We aren't trying to have a kid but if it happens we will be extremely happy but I have taken a few tests and come have been negative & some positive. I went to planned parenthood & they said I need a blood test to make sure. Any of you girls ever not show up on a urine test & only a blood test? & if I am pregnant what is my first step.